Exactly. Double or multiple coated conventional film is all
coated on one side. X-ray film is often coated on both sides of
the support. Some film was also coated with two emulsions, one
for the x-rays the other for the visible light emitted by the
fluorescent screen meant to boost the x-ray image so as to reduce
x-ray exposure.
Conventional black & white film is sometimes coated with two
or three emulsions but sometimes the emulsions are mixed together
before coating so there is only one coat but with a different
characteristic than the separate emulsions.
Helge's memory is the same as mine, scattering is due to the
particles suspended in the emulsion. Not only is it greater for
thick emulsions but also for coarse grain emulsions.
In the 1930s motion picture sound recording often made use
of ultra-violet light in the recorder combined with yellow dye in
the emulsion of the recording film to limit penetration of the
recording light to the surface. The idea was to reduce scattering
in the emulsion so as to improved high frequency response and
reduce distortion. The compromise was between this and being able
to get enough light to the film to get correct exposure.
Eventually, improved film made this technique obsolete.
Photographic sound recording requires very high resolution, at
least 30 lines/mm at 35mm sound speed (24 FPS= 18 inches per
second). on the print for moderate fidelity.
On 7/20/2018 9:21 PM, Kurt Griffin wrote:
Just to add to potential confusion: X-ray film traditionally had emission on
both sides of the support base, the better to capture said X-rays; essentially
higher speed and the resolution wasn’t impacted for the purpose. In my time,
Tri-X was only coated on one side, so any multi-coat must refer to layers.
Kurt in SoDak
On 20 Jul 2018, at 16:18 , Helge Nareid <hn.groups@xxxxxxxxxxxx> wrote:
